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Dimmers: Leading Edge vs Trailing Edge

Dimmers: Leading Edge vs Trailing Edge

LED Dimmers

If you're shopping for dimmable LED light bulbs for your home, office or shop, it is absolutely crucial that you ensure your bulbs and dimmer switches are compatible with each other to prevent issues like the dimmer switch buzzing and lights flickering. Not all LED dimmers are the same - two regular mains dimmer switches that visually look identical can actually be completely different.

LED Dimmer Types

When looking at regular mains dimming, there are two main types of light dimmer to look out for. These are known as trailing edge and leading edge. Other types of dimming including Dali and digital do exist - however these are most often used in much more complicated lighting solutions than tends to be found in homes and offices.

Together, leading and trailing edge dimming technologies are referred to as phase cutting dimmers and they are named after the part of the AC wave that they cut off to dim the lighting.

Dimmer switches using leading edge technology cut off the front edge of the half cycle of each AC wave, whereas trailing edge dimmers cut off the second half of each half cycle.


Leading edge

Trailing edge

Dimmable LED lamps are available in both leading and trailing edge versions depending on the manufacturer, so it is important to be sure what LED dimmer type you're looking at to make sure that they are suitable for your specific application.

Why does my dimmer switch buzz?

If your dimmer switch is buzzing, this can mean that your LED lamps are not compatible with the dimmer switch you have installed. Common causes of problems are not meeting the minimum load of the dimmer, overloading the dimmer with lamps that are of too high a wattage, or using the wrong type of lamps for the dimmer switch you have; for example, using trailing edge lamps with a leading edge dimmer.

Things to note when dimming LEDs

  • Not all LED lamps are dimmable - make sure you check the product's specifications before you make a purchase
  • If you already have a dimmer switch installed but are unsure of the dimmer type it uses, it would be worthwhile checking with the manufacturer of your dimmer switch before looking into dimmable LED bulbs as incompatible combinations can cause the LED bulbs to flicker and the dimmers to buzz
  • Make sure to check that the minimum and maximum loads of the dimmer switch is suited for the number and combined wattage of the lamps and light fittings in the circuit
  • Do your research to make sure your lamps and dimmers are suitable for the same type of dimming. Where possible, it can help to match your lamp manufacturer to your dimmer manufacturer. For example, we would recommend using a BG dimmer switch with BG Luceco's dimmable lamps
  • If matching your lamp manufacturer to the dimmer's manufacturer isn't practical or you want more flexibility in case you change lamp manufacturer in the future, you can consider the Hamilton LEDIT-B100 dimmer module or the Click Scolmore MD9014 Dual Mode dimmer module. These modules allow you to easily choose between leading or trailing edge dimming depending on your application.

LED Dimmers

Here at the Electrical Counter, we offer a wide range of single dimmer switches, double dimmer switches, and LED lights from all the major brands including BG Electrical, Click Scolmore, Hamilton and many more. If you're not sure what LED dimmer would be best for your requirements, get in touch with us today.

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